Synthesis and reactions of 1-thianaphthalenes.

Abstract

Treatment of 1-methyl-4-phenyl-1-thio-2H-chromenium perchlorate (2) with sodium hydride yielded a dimeric compound 4 and two rearrangement products 5 and 6 via unstable 1-methy1-4-phenyl-l-thianaphthalene (3). On heating with potassium hydroxide in ethanol, 1-methy1-2, 4-dipheny1-1-thio-2H-chromenium perchlorate (9) gave a dimeric compound 13 and two ring-opened products 11a and 12a, but no rearrangement product. On the other hand, 2-cyano-l-methy1-4-phenyl-1-thianaphthalene (20) prepared from the corresponding 1-thiochromenium salt 19 by treatment with triethylamine in ethanol was quite stable, and it is the first example of a stable and crystalline 1-thianaphthalene.Reactions of the 1-thianaphthalene 20 with electrophiles such as tetracyanoethylene, maleic anhydride, and 4-phenyl-1-thianaphthylium perchlorate gave the dimeric compound 23. However, the treatment of 20 with dimethyl acetylenedicarboxylate yielded a new ring expansion product 27 having a sulfur-containing nine-membered ring.